928 Wheel Size

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I am looking at a set of 18 inch wheels for a 1981 928. I have found a set that are 8inch x ET50 fitted with 225/40/18 and 10 x ET65 with 285/30/18 for the rears. Does anyone with a 928 know if they will fit okay? I have heard that ET65 is the standard offset, and you ideally dont want to go less than ET55 but some have run ET50 on the front?

I am throwing up between those or going back to phone dials. Its a 1981 but has the S4 brakes updated, does anyone know if 16 inch phone dials will clear those brakes? I know, completely different direction but working out which look I would rather.

Lastly there was a company making 18 inch phone dials overseas, anyone know where?

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GSE73 I've got a 1980 928 with BBS mags and 235/40xR18 (et45) The front tyres scrape slightly during hard cornering and in the rear there's still a bit of clearance for a wider tyre so I would say the sizes you mention will probably fit ok. They do look better with wider tyres on the rear.

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In regards to steering feel the ET is very important & as you have correctly mentioned , the standard ET ( wheel offset ) is 65mm , going to a ET 50mm ( 15mm per side difference ) = 30 mm total difference will result in a lot of tram tracking , particularly after the new front tyres settle in ( a few thousand kms from new ) , basically the car will follow irregularities in the road surface , some of which will shock you when it catches you by surprise as you are driving along even at 50Kmh and at 110 or 120Kmh on a free way you will be compensating with lots of steering inputs ( with you're hands ) which at first is not that noticeable , but after an hour or so you will know what I mean , its very tiring

But if you drive a 928 ( any ) from the very beginning with the wrong ET front wheels ( 13 mm or 15 mm incorrect ET ) , you will be none the wiser as this is the only reference point you have & you will think , gee these cars steer a bit funny

Google } Scrub Radius

In regards to the 16" dia 928S cast & painted " Telephone style" wheels , these were fitted by Porsche as standard to the 928S 4.7L from 1980 to 1985 inclusive and were an option on the 928 4.5L > 1982 , we have a 1984 928S here at the moment with the standard Telephone wheels

From model year1986 ( F vin letter ), the 928S had as standard the Brembo front "mid size blacks " 4 piston alloy front brake calipers ( 928S4 style ) and the Brembo 4 piston " small size blacks " on the rear , Porsche was not happy with the very very tiny clearance that the thicker cast alloy rimmed telephone style wheel gave on the front ,so Porsche installed as standard the more expensive Fuchs forged wheels & these gave a better clearance for the "mid blacks ", thats because being forged the rim thickness was less

I have test fitted a single telephone wheel onto one side ( front ) of a 928S4 and it was very tight & the wheel weights ( stick on) would not clear the brake caliper at all , but if you are fitting caliper adapters to a early 928S to fit S4 front brakes , it may be either a slightly better clearance or slightly worse ( fractions of a millimeter )

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I currently have some rather ordinary looking Cup style wheels on it. They look to be an 9J x ET47 in the rear and either 7.5 J x ET52 (or 57 hard to read) on the front. Does that sound right, I am not sure if they are original Porsche or replicas - how do you tell?

Bruce - does tram tracking start gradually moving away from ET65 or is there a pronounced point in which it starts. Some articles I have read said ET55 is acceptable but issues start from going below ET50. Is that your experience or is sticking to the ET65 critical? This is he only 928 I have driven so like you mentioned I have no other reference point.

The brakes have obviously been updated later in its life. Maybe that's when the Cup wheels were also put onto it.

Maybe refurbishing the Cup wheels might be the better if I can't source another option.

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Genuine Porsche 17" dia cup 1 or genuine Porsche 17" dia cup 2 wheels have the ET number & the width number cast into the outside of the wheels on either side of the valve stem hole , aftermarket cup wheels do not . So that means ( Front ) genuine Porsche Cup 1 or genuine Porsche Cup 2 wheels are 65 mm ET , either for the 928GTS or the 968

Genuine Porsche 928 & 968 Cup 1 & Cup 2 wheels are }

Front = 7.5" X 65 ET X 17"
Rear = 9" X 55 ET X 17"

You will probably find you have the Mille Miglia aftermarket wheels , because they came in 7.5 " X 52 ET & these were very common here in Australia 20 + or so years ago because they were so cheap , but they are heavy & they bend relatively easily in both planes ( oval/bent rims & twisted spokes ) , we have thrown out heaps of them over the last 20 years

ET 55 mm is 10mm out ( in relation to steering feel I find it crap to drive in relation to 65 mm ET)

ET 52mm is 13mm out ( that's just a little bit more crap to drive )

ET 50 mm is 15mm out ( that's just a bit more more crap to drive)

Its just mathematics , look up / Google " Scrub Radius" , you will see why it becomes at time a bit dangerous to drive , I am used to driving Porsche's with the wrong ET ( poor choice of wheels ) and in certain road conditions it still catches me out , meaning the steering wheel will for a split second wants to violently turn into oncoming traffic or the other direction

It makes no difference to me what people choose , just understand how bad it can make the car feel

If you drove you're 928S with a correct set ( 65mm ET ) front wheels and new tyres ( not crap tyres , but something that is a decent tyre ) you will never ever go back to any other ET , its that good

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Be careful with the cast alloy D90's as shown in the photo above ( light blue 928S )because the correct ones for a 928 are very rare , where as the incorrect ones are quite common & will not work or even fit over the 928S4 mid blacks front brake calipers

Only the 1990 & 1991 year model 928GT had the 928 specific wheels in the cast and painted D90 style , for the 1990 & the very rare 1991 928S4 , those cast and painted wheels were an option only M400 & I have never seen a 1990 or a 1991 928S4 that came with those wheels as an option

Note } the 1990 & 1991 928S4 had as standard the Fuchs forged and anodized wheels 16" x 7" & 16" x 8" & yes these fit over the 928S4 brakes & they are very light as well

---------------------------------------

The ones you do not want in that D90 style are the wheels from a 1989 - 1991 944S2 ( very common ) or from the 964 1990-1992

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Yes they do make them, I made contact and they are an eye watering $1,099 (Canadian $) a wheel and about $900 to freight. Close to $6k AUD to have them landed in Australia (plus tyres!). Not sure my threshold for wheels stretches that far!

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The way I look at it is Porsche spent millions of dollars and man hours getting the design right the first time which also includes the way it handles and drives with a certain size wheel/tyre combo so why bother spending a couple of grand buying a different combo only to turn the car from a great handling car to an PITA handling car.

As Bruce said the wrong size combo can really take away the experience of what should be a great handling vehicle.

Had the wrong combo on my old 930 and talk about tram tracking, f@#k it was awful but when I went back to originals wow what a difference.

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The way I look at it is Porsche spent millions of dollars and man hours getting the design right the first time which also includes the way it handles and drives with a certain size wheel/tyre combo so why bother spending a couple of grand buying a different combo only to turn the car from a great handling car to an PITA handling car.

As Bruce said the wrong size combo can really take away the experience of what should be a great handling vehicle.

Had the wrong combo on my old 930 and talk about tram tracking, f@#k it was awful but when I went back to originals wow what a difference.

Will never make that mistake again.

I agree, unfortunately the original wheels aren't on the car and we aren't certain the original 16inch wheels (phone dials) will clear updated brakes. So I would return to stock but that doesn't seem an option. Although another set of larger diameter wheels with the same offset should do the trick - if I can find them...

2 hours ago, ANF said:

Does that allow for GST and import duties? Yes very expensive, although new genuine 928 wheels would be similar.. Good luck!

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I agree, unfortunately the original wheels aren't on the car and we aren't certain the original 16inch wheels (phone dials) will clear updated brakes. So I would return to stock but that doesn't seem an option. Although another set of larger diameter wheels with the same offset should do the trick - if I can find them...

Nope!

add another 15% + then!!

Jump on Ebay and Gumtree a couple or forged Fuchs manhole covers on their.